Evaluating Direct Dial Data Providers for Clay Integration

Hi, we are looking for the best way to enrich people with direct dial data (work phones). We have tried the different providers, which were mentioned in a Clay Article - People Labs, BetterContact and have been most convinced by Bytemine. The hit rate for direct numbers seems to depend a lot on industry, region etc, which is not very satisfying. Doing some research, I read that ContactOut, Infrobel Pro, Lusha and Boldata have solid databases for direct lines in the US and Europe. Some have an API, some are already integrated in Clay (Contacout only provides mobile numbers). Can you tell me, which of these is most recommended for Clay?